Rory McIlroy's Masters preparations suffered another blow as he struggled to an opening 74 on his maiden appearance in the Valspar Championship.

McIlroy's only birdie came courtesy of holing a bunker shot on the seventh, his 16th hole of the day, while two bogeys and a clumsy double-bogey seven on the fifth left him three over par.

The 28-year-old began the season in superb form with a tie for third in Abu Dhabi and a runners-up finish in Dubai, but missed the cut on his first PGA Tour start at Pebble Beach and followed that with a tie for 20th in the Genesis Open and 59th in the Honda Classic.

McIlroy told a pre-tournament press conference at Innisbrook that he was "totally ready" for the Masters and felt he would have a good chance of the victory he needs at Augusta National to complete the career grand slam if the first major of the year got under way this week.

But his performance on Thursday told a somewhat different story after starting from the 10th with 10 straight pars before failing to get up and down from a greenside bunker on the second.

Worse was to come on the fifth after a wayward drive into the trees forced McIlroy to pitch out sideways, a mistake he compounded by taking four to get down from just short of the green.

And although the birdie on the seventh repaired some of the damage, McIlroy dropped another shot on his final hole to finish three-over par, six shots off the early clubhouse lead shared by Whee Kim and Kelly Kraft.

Masters champion Sergio Garcia had to settle for an opening 70 after dropping two shots in his last six holes, with Ryder Cup team-mates Justin Rose and Luke Donald also finishing one under par.

Like McIlroy, former world number one Tiger Woods is making his debut in the tournament and playing his fourth PGA Tour start since undergoing spinal fusion surgery last April.

The 42-year-old got off to an ideal start by almost chipping in for an eagle on the par-five first and tapping in for an easy birdie, but bogeyed the fourth after misjudging the swirling wind and firing his tee shot 20 yards over the green.

Woods was far more accurate with his approach to the seventh and saw his ball clatter into the pin, but was unable to hole the subsequent birdie putt from six feet.

The 14-time major winner did hole from twice the distance on the next for birdie, but gave the shot straight back on the ninth after failing to get up and down from a greenside bunker.

At level par, Woods was four shots off the clubhouse lead held by Canada's Corey Conners.